Archaeal complex II: ‘classical‘ and ‘non-classical’ succinate:quinone reductases with unusual features

AbstractReversible succinate dehydrogenase (SDH) activities have been ubiquitously detected in organisms from the three domains of life. They represent constituents either of respiratory complexes II in aerobes, or of fumarate dehydrogenase complexes in anaerobes. The present review gives a survey on archaeal succinate:quinone oxidoreductases (SQRs) analyzed so far. Though some of these could be studied in detail enzymologically and spectroscopically, the existence of others has been deduced only from published genome sequences. Interestingly, two groups of enzyme complexes can be distinguished in Archaea. One group resembles the properties of SDHs known from bacteria and mitochondria. The other represents a novel class with an unusual iron–sulfur cluster in subunit B and atypical sequence motifs in subunit C which may influence electron transport mechanisms and pathways. This novel class of SQRs is discussed in comparison to the so-called ‘classical’ complexes. A phylogenetic analysis is presented suggesting a co-evolution of the flavoprotein-binding subunit A and subunit B containing the three iron–sulfur clusters

Hydra: practical metadata security for contact discovery, messaging, and voice calls

Protecting communications’ metadata can be as important as protecting their content, i.e., recognizing someone contacting a medical service may already allow to infer sensitive information. There are numerous proposals to implement anonymous communications, yet none provides it in a strong (but feasible) threat model in an efficient way. We propose Hydra, an anonymity system that is able to efficiently provide metadata security for a wide variety of applications. Main idea is to use latency-aware, padded, and onion-encrypted circuits even for connectionless applications. This allows to implement strong metadata security for contact discovery and text-based messages with relatively low latency. Furthermore, circuits can be upgraded to support voice calls, real-time chat sessions, and file transfers - with slightly reduced anonymity in presence of global observers. We evaluate Hydra using an analytical model as well as call simulations. Compared to other systems for text-based messaging, Hydra is able to decrease end-to-end latencies by an order of magnitude without degrading anonymity. Using a dataset generated by performing latency measurements in the Tor network, we further show that Hydra is able to support anonymous voice calls with acceptable quality of service in real scenarios. A first prototype of Hydra is published as open source

Sabotageangriffe auf Kommunikationsinfrastrukturen: Angriffstechniken und Abwehrmaßnahmen

Sabotageangriffe, im Englischen auch als „Denial of Service Attacks (DoS-Attacks)“ bezeichnet, zielen darauf ab, die Verfügbarkeit bestimmter Systeme oder Dienste für berechtigte Nutzer zu reduzieren bzw. die entsprechenden Systeme und Dienste vollständig außer Betrieb zu setzen. In diesem Beitrag wird ein Überblick über in Sabotageangriffen verwendete, grundlegende Techniken und prinzipielle Abwehrmaßnahmen gegeben

Dependence of aptamer activity on opposed terminal extensions : improvement of light-regulation efficiency

Aptamers that can be regulated with light allow precise control of protein activity in space and time and hence of biological function in general. In a previous study, we showed that the activity of the thrombin-binding aptamer HD1 can be turned off by irradiation using a light activatable "caged" intramolecular antisense-domain. However, the activity of the presented aptamer in its ON state was only mediocre. Here we studied the nature of this loss in activity in detail and found that switching from 5'- to 3'-extensions affords aptamers that are even more potent than the unmodified HD1. In particular we arrived at derivatives that are now more active than the aptamer NU172 that is currently in phase 2 clinical trials as an anticoagulant. As a result, we present light-regulatable aptamers with a superior activity in their ON state and an almost digital ON/OFF behavior upon irradiation

Ein dänisches "Beschäftigungswunder?" (A Danish “employment miracle”)

"Denmark is one of the European countries which has been able to reduce unemployment drastically in recent years; the unemployment figure has fallen by more than 120,000 since its peak of 340,000 in 1994. This success deserves particular attention because the policy followed in Denmark differs very clearly from that in the other countries with employment policy success; there is no sign of an accentuated liberalisation of the labour market, nor does the secret behind the Danish success lie in promoting part-time work or enforcing reductions in working time. As is shown in this report, the reduction of unemployment goes back to several policies acting in combination which tackled the problem almost simultaneously: a fiscal policy which first (in 1994) gave an expansionary impulse of a total of 1.2 % of the GDP and reformed the tax and social security systems; a labour market policy which increased the pressure on people to take up employment, used existing instruments (early retirement regulations) to a greater extent and developed new ones (sabbatical models), thus reducing the labour force potential by some 100,000 at short notice; and finally a wages policy which pursued a moderate course in spite of strong economic expansion and arranged wage determination more flexibly. One key to success is the fact that a stronger macroeconomic growth came about in Denmark not least as a result of this change in policy, but the higher growth explains the increase in employment only partially; the other policies also contribute to this. The method used to solve the employment problem in Denmark can not easily be applied to Germany, in view of the difference in size alone and the special problems of eastern Germany. Nevertheless this report emphasises three elements of reform that could also point the way ahead for Germany: firstly the concerted procedure mentioned which also led to the various measures having an increased effect especially in the initial phase. Secondly keeping to the schedule. Virtually all the measures taken were limited in time and in the following period the plans for phasing them out were also adhered to. Thirdly Denmark is an example of how a high level of social security need not stand in the way of reducing unemployment, provided that the other conditions are appropriate for this. In particular the high level of basic security probably contributed to the acceptance of the cuts which are also unavoidable in Denmark." (Author's abstract, IAB-Doku) ((en))Arbeitslosigkeitsbekämpfung, Beschäftigungspolitik, Arbeitsmarktentwicklung, Arbeitskosten, Sozialpolitik, Dänemark

Einfluss der Schmierung auf die Gestaltfestigkeit der Passverzahnung

Die Dimensionierung von Passverzahnungen muss verschiedene Aspekte berücksichtigen. Dazu gehören neben der Gestaltfestigkeit auch die Verschleißfestigkeit und die dazwischen agierende Reibdauerschädigung. Mit diesem Betrag wird für die Wahl eines geeigneten Festigkeitsnachweises Licht in den Bereich zwischen Gestaltfestigkeit und Reibdauerschädigung gebracht und der Einfluss der Reibbeanspruchung im Kontakt auf die Beanspruchung in der Zahnfußausrundung geklärt.The dimensioning of splined shaft-hub connections takes account of fatigue strength and wear plus the blended fretting load. Within this paper a detailed view is given on friction and their impact on fatigue strength in the foot root

Neuer Prüfstand für zügige Torsionsbeanspruchung

Die experimentelle Untersuchung von Maschinenelementen ist einer der Schwerpunkte des Institutes für Maschinenwesen. Der umfangreiche Prüfstandspark wurde nun um einen weiteren Prüfstand für zügige Torsionsbeanspruchung ergänzt. Dieser Prüfstand ermöglicht die kontinuierliche Torsion von Prüflingen auch über große Verdrehwinkel.One of the focuses of the in stitute of mechanical engineering is the experimental study of machine elements. The large park of test plants is now extended by another test plant for fast torsional stress. This test plant allows the continuous torsion of samples for large torsion angles